Study design and procedure
This study was a randomized crossover (double-blind) design. Participants and researchers were blinded from the administered fluid type. Participants were randomly assigned to receive either dextrose (D) solution or sodium dextrose (Na-D) solution. Randomization took place immediately after the participants had been confirmed to be eligible for entering the study. The randomization code of the drink, was not made available to anyone involved in conducting or evaluating the study, and was released after the blind review and the freezing of the final database. After randomizing, the study was divided into three phases, as shown in Fig. 1. Assessment of health status, dietary intake, measurement of body composition, baseline blood glucose, baseline VO2 max, and baseline sprint speed were evaluated in phase I. In phase II, we measured the blood glucose before the participants drink the dextrose or sodium dextrose supplementation. We asked the participants to sprint before received the solution, then we record the time and calculating the VO2max. After that, we give one type of solution (dextrose or sodium dextrose). In order to have a comparison of the post supplementation effect, the participants repeated the previously mentioned procedures in this phase II. Phase III was similar to phase II except for the nutritional supplementation. The participants could receive either dextrose or sodium dextrose in phase II, and the opposite alternative in phase III. This trial was conducted at UNM Banta-Bantaeng, Makassar, Indonesia, from April 2019 to May 2019.
Supplement preparation
The supplements consisted of dextrose (D) or sodium dextrose (Na-D). Glucose is a monosaccharide, which acts as an essential energy source through aerobic or anaerobic metabolism. Dextrose or D-glucose is an aldohexose stereoisomer of glucose. It is the most commonly occurring isomer of glucose in nature. Our pharmacist used 15 g of dextrose anhydrous to make a 150 ml dextrose 10%, with pH 5.27. Another 150ml Sodium dextrose solution consisted of 10% dextrose, added with 20mM of sodium. The material is taken from Japan (Otsuka Holdings Co., Ltd.) and all of the entire mixing process was supervised by Akademis hospital licensed pharmacist.
Participants
Sample sizes for this research are twenty one, and it was calculated by equation n= [ {(Zὰ + Zᵦ) X Sd } / d ]2 , with Zὰ = 1.96; Zᵦ = 0.842; Sd= 28.2; d=10. Random allocation was performed using a random electronic generator via https://www.random.org/lists/. Our pharmacists staff were responsible to generate the random allocation sequence, enrolled participants, and assigned participants to interventions. After assignment of interventions, all of the participants and us, were blinded. A total of 50 male outfield academy soccer players were screened for the study. Thirty-two participants entered into the inclusion criteria. All were healthy and free of injury in the three months preceding the study. Three participants refused to join, and 6 were dropped out. Twenty-two participants participated (age, 19.6 ± 1.1 years; height, 165.7 ± 5.25 cm; weight, 52.5 ± 8.47 kg; body fat, 12.5 ± 4.68 %; muscle mass, 82 ± 4.7 %; BMR, 1346 ± 147.0 kcal) in the study and were successfully analysed until the end. Prior to enrolling in the study, each participants’s physical examination and health history were taken. Eligibility criteria were healthy men soccer players between 18 and 23 years of age, who exercised on average between 8 and 12 h per week the last month prior to inclusion. All participants were within the last meal four hours prior to the test. Exclusion criteria were the use of amylase supplement, suffering from fever and diarrhoea, using laxative agents within 24 h, consuming CHO absorption inhibitors, caffeine, creatinine, beta alanine, sodium bicarbonate supplement within 24 h, mean arterial pressure <65mmHg, knee or muscle injuries, history of diabetes mellitus and heart disease, going through the ketogenic diet program, history of gastrointestinal surgery, and total body fat percentages > 30%. Participants who were currently taking any other dietary supplement, sports drink, or functional food intended to enhance performance or muscle mass, or had taken any of these in the previous week, were also excluded.
The study was approved by the Faculty of Medicine Hasanuddin University Research Ethics Committee with the reference number 214/UN4.6.4.5.31/PP36/2019. All research was performed in accordance with relevant regulations supervised under Hasanuddin University and department of sport science, Makassar State University. Written informed consent was obtained from all participants prior to inclusion.
Intervention and procedures
The participants were instructed to abstain from exercise 24 h prior to the testing in phase I, II and III, and they arrived at the field track by car, motorcycle or by public transportation. They were recommended to maintain usual eating pattern 48 h before the test and had a last meal 4 hours before the phase I. In addition, they were told to refrain from coffee and kind of sports drink 48 h prior to the test.
Dietary intake was collected using two days food recall. BG were measured from capillary blood glucose from the fingertip and immediately analysed (Aviva; Accucheck, Roche Diagnostics, Indiana, U.S.A), blood pressure was measured using aneroid sphygmomanometer (R1 shock-proof; Riester, Jungingen, Germany), heart rate was measured with wrist band pulse monitor (Bluetooth 4.0 wireless sport heart rate monitor WP290; Egoman, Shenzen, China), body weight, muscle, fat, water, metabolic rate was measured using the body composition analyzer (BC-545N; Tanita, Tokyo, Japan), body height was measured using a stadiometer (HR-200, Tanita, Tokyo, Japan), sprint speed were measured using a digital stopwatch (S23589 S23589P1; Seiko, Tokyo, Japan)
Participants were instructed to refrain from strenuous physical activity in the 2 days preceding trial sessions and recorded all food consumed in the 2 days before the trial. Food records subsequently were analysed using professional German nutrition software (EBISpro, Nutrisurvey 2007). On arrival at the field, pre supplementation capillary blood samples were collected, and then all players run for 2x100 m and calculated the VO2max using Uth-Sorenen-Overgaard-Pedersen formula and sprint speed was recorded. After doing the baseline measurement, each player waited for 15 minutes in order to consume either dextrose or sodium dextrose solution, and then waited for 15 minutes to have another subsequent capillary blood samples measurement. After that, the players run for 2x100 m, recorded the VO2max and sprint speed. The players remained in a rested state for 120 minutes as a crossover washed-out period, and then did the same protocol with a different solution.
Statistics
Descriptive statistics were used to characterize the participants (mean, standard deviation (SD), with 95% confidence interval, and significance was accepted at p < 0.05. Data were checked for normality as indicated by the Shapiro–Wilk test. Paired samples t tests were used for comparison before and after condition in blood sugar, VO2max and sprint speed. All reported p-values were based on two-sided tests. Exact values of p < 0.05 were considered statistically significant. The data was analysed using IBM SPSS Statistics 25 for windows (SPSS Inc., Chicago, Illinois, USA). The sample size was selected based on an a priori power calculation. Accordingly, with a type I error of 0.05, power analysis revealed that for a 2-tailed paired data Student t test a sample size of 21 individuals is adequate to achieve a power of >80%. To interpret the magnitude of effect, Cohen’s d effect sizes (±95% confidence limits) were estimated using a purpose built spreadsheet, with effect size thresholds set at <0.20, >0.50, and >0.80 for small, moderate, large, effects respectively.